Quercetin loaded gelatin films with modulated release and tailored anti-oxidant, mechanical and swelling properties

Quercetin, a flavonoid widely diffused in fruits and vegetables, is known for its good pharmacological qualities, such as anti-oxidant and anti-inflammatory properties. In this work, we loaded quercetin on gelatin films with the aim to develop materials with tailored anti-oxidant, mechanical and stability properties. To this purpose, gelatin films at increasing flavonoid content were prepared using two different solvents, namely H2O/EtOH (EtOH films) and DMSO (DMSO films). Quercetin content increased up to about 3.8 and 1.8 wt% in DMSO and EtOH films, respectively. The use of DMSO as solvent prevents the partial regain of collagen triple helix structure during gelling of gelatin sols and results in remarkable extensibility of the films. At variance, EtOH films display X-ray diffraction patterns and DSC plots in agreement with the presence of triple helix structure, and exhibit reduced swelling and increasing mechanical properties on increasing quercetin content. Moreover, their values of denaturation enthalpy indicate the presence of chemical interaction between the flavonoid and gelatin, which can be responsible of their lower quercetin release in PBS in comparison to DMSO films. The flavonoid release is sustained for both series of films and occurs through anchorage to gelatin nanoparticles. Moreover, both DMSO and EtOH functionalized films exhibit relevant anti-oxidant properties, in agreement with their RSA levels, which are comparable to that of pure quercetin.